Controlling the charging of a rechargeable electrical energy storage device, such as a rechargeable battery, by an electrical energy source, is a requirement that is rather commonly encountered.
The generally favored technique where the signal from the source is subject to substantial variation is the incorporation of a voltage regulator into the control apparatus to lower the voltage of the signal from the source to the approximate level of the fully charged voltage of the device. Then, as the device is charged, the current from the regulator to the device will decrease as the voltage of the device increases, and will be substantially terminated by the matched voltage levels when the device is approximately fully charged. The foregoing technique is, due to the regulation of the voltage level, essentially a constant voltage technique.
A constant current technique, at times, is also used. This technique, by way of example, may be implemented by providing a source with a voltage which is much greater than the fully charged voltage of the storage device. Disadvantages in this technique result from the typical lack of self-regulation and, for some applications, a need to adjust the current to the device at certain stages in the charging process.
In the last few years, with increased experimentation with, and usage of, solar energy, attempts have been made to implement charging control in the context of the charging of an electrical energy storage device, such as a rechargeable battery, by a solar panel. Perhaps the most common implementation provides a regulator to provide essentially a constant voltage, and a self-regulating situation in the charging mode.
Another technique, which has met with some success, and which carries certain advantages, is disclosed in U.S. application Ser. No. 113,936, having John W. Yerkes and Terry Staler as inventors, and Atlantic Richfield Company as assignee, and now abandoned.
As disclosed in such application, that technique entails a direct solar panel to battery connection until a charging termination threshold is reached at the point of such connection, at which time the connection is terminated. Further, during such charging, at certain intervals, breaker apparatus causes a disconnection so that the disconnected solar panel and battery can be tested for whether the ratio of their voltage levels is such that a reconnection should be avoided to prevent discharging of the battery through the solar panel (e.g., at night). Where the charging prevention ratio does not obtain, but due to the charging termination threshold having been reached, the unconnected status does, reconnections, at intervals, occur so that charging can be resumed when such is required.
This is all disclosed in detail in the above-identified application.
According to another basic approach, direct charging through a relay and, at other times, trickle charging through a regulator, is employed. As conventionally proposed and implemented, this variation maintains the direct connection independently of the status of the solar panel, where a charging termination level has not been reached. In addition, once such level has been reached and a direct charging has been terminated, resumption of direct charging typically will not occur until after the disconnected signal at the solar panel has passed below a chosen level (e.g., at night) and, subsequently, passed above that level (e.g., when the sun rises).
The control of discharging of an energy storage device, such as a battery, through a load, in connection with charging control, is also of considerable interest, both generally, and in the context of the charging of a battery by a solar panel. For example, automatic, electronic disconnection of the battery and the load, when the battery voltage passes below a discharge prevention threshold, and automatic electronic reconnection, when the battery voltage passes above a higher load reconnection threshold (after significant recharging), has been employed. In particular, it has been employed in the context of the direct and regulated charging, described in the above paragraph. Such automatic, electronic control is in keeping with the thrust toward fully automatic control.
It might also be noted that in charging and discharging control apparatus, e.g., along the lines described immediately above, transistors and zener diodes are among conventional devices that are commonly used in conventional arrangements.
The present invention incorporates two modes of charging in a context which breaks the coupling for one mode to determine whether the coupling for that mode should be continued or the coupling which permits the other mode should be selected. It further incorporates discharging control in a context which requires manual intervention at a significant juncture. In addition, the charging control is accomplished with the aid of a configuration of a number of electronic devices in a form which provides simplicity of design and operation at the crux of such charging control.
In accordance with the invention, apparatus is provided for controlling the charging of a rechargeable electrical energy storage device for generating a storage device electrical signal, by an electrical energy source for generating a source electrical signal, which source has a charging output terminal and which device has a charging input terminal. Such apparatus, in accordance with the invention, includes: relay means for electrically coupling the charging output terminal of the source and the charging input terminal of the device to permit charging of the device by the source through the relay means; regulator means for electrically coupling the charging output terminal of the source and the charging input terminal of the device to permit charging of the device by the source through the regulator means and for providing an electrical regulated output signal for such charging; signal-testing means coupled to the relay means for receiving the storage device electrical signal and for providing an electrical output signal for terminating such relay means coupling in response to the storage device electrical signal; selector means, coupled to the relay means and responsive to the storage device electrical signal, for receiving the source electrical signal and for providing an electrical selector signal for selecting the relay means coupling to permit charging through the relay means and for selecting the regulator means coupling to permit charging through the regulator means in response to the source electrical signal and the storage device electrical signal; relay breaker means coupled to the relay means for providing an electrical relay breaker signal for breaking such relay means coupling after such coupling for a predetermined period of time; and relay driver means coupled to the relay means for providing an electrical control signal for controlling such relay means coupling in response to the selector signal and the breaker signal.
In accordance with more detailed features, the selector means may include a silicon controlled rectifier operating as a switch, with the gate terminal of the SCR acting as a relay means coupling termination terminal, and with the anode terminal of the SCR acting as a relay means coupling control terminal for initiating such relay means coupling when the source electrical signal passes a predetermined level, for terminating such coupling when the storage device electrical signal passes a predetermined level and for maintaining such coupling during the course of such coupling until the initially described breaking by the breaker signal; the relay breaker means may include an output transistor in parallel with the SCR having an output terminal directly connected to the SCR anode terminal to provide the breaker signal; the relay driver means may include a zener diode in parallel with the SCR, with the signal at the anode of the SCR having to overcome the breakdown voltage of the zener diode to initiate and maintain such relay means coupling; and the selector means may additionally include a resistor having a terminal directly connected to the anode terminal of the SCR, for directly receiving the source electrical signal at the other terminal thereof and for providing a series connection to the anode terminal for the source electrical signal.
In accordance with other more detailed features of the initially described apparatus, the relay means may include a switch for directly connecting the charging input terminal of the storage device and the charging output terminal of the source. Also, the controlling of the relay means coupling may include reestablishing such coupling in response to the selector signal upon the breaking, as initially described, of such coupling.
In accordance with additional aspects of the initially described apparatus, such additional aspects for controlling the discharging of the electrical energy storage device through a load, such apparatus may further include: circuit breaker means for electrically coupling the charging input terminal of the electrical energy storage device to the load to permit such discharging through the load, wherein the circuit breaker means includes an electronically and manually operated switching means; and circuit breaker, breaker means coupled to the circuit breaker means for receiving the storage device electrical signal, for terminating such coupling by the circuit breaker means in response to the level of the device electrical signal falling below a predetermined level and for substantially preventing the reestablishing of such coupling until the level of the device electrical signal rises above a predetermined level and such switching means is manually operated.
In accordance with other aspects of the invention, charging and discharging control apparatus in accordance with the invention may be incorporated into solar to electrical energy conversion apparatus which includes a solar panel as an electrical energy source, and a rechargeable electrical energy storage device which is charged by the solar panel.
Charging control methods, in accordance with the invention, are directed to the methods of operation of the charging and discharging control apparatus, including electronic methods, which can be long-term without human intervention.